X-ray tube



has i, 1943. A. BOUWERS 2,320,559

X-RAY TUBE Filed Jan. 15, 1941 IN'VEN TOR ALBERT BOUWERS Arromvsv.

Patented June 1, 1943 v X-RAY TUBE Albert Bouwers, Eindhoven, Netherlands; vested in the Alien Property Custodian Application January 15, 1941, Serial No. 374,582 In the Netherlands October 6, 1939 7 Claims. (01. 250'-90) There are protected X-ray tubes which are arranged in an envelope filled with an insulatquently, the whole of the tube and the envelope may have. smaller dimensions than if the insulating medium within the safety envelope consists entirely or partly of air. However, the use of an insulating liquid also entails disadvantages which are brought about'by the .development of heat in the X-ray tube when it is loaded. i

In protected tubes having-air-insulation the heat is mostly conducted to a metal body extending outside the sube and is subsequently given ofl to the shield by radiation and convection.

The surface of this shield is of such size that it can easily give oil the heat to the surrounding air and its temperature does not rise excessively.

When an insulating liquid is used the transfer of heat from the cooler to the envelope is principally effected by convection. This means that the liquid which makes contact with the cooler of the X-ray tube is heated and gives ofi heat to cooler parts of the apparatus with which it makes contact later. These parts may also include those for which heating may be harmful. Consequently, it may be necessary to take measures to prevent this.

This particularly applies to those cases in which the X-ray tube, together with other parts of the X-ray apparatus such as the transformer which supplies the high voltage to the tube, is

arranged in a common housing filled with oil.

If no special measures are taken, these parts are heated during operation of the apparatus by the energy which is transformed into heat in the X-ray tube. In such instances, the auxiliary apparatus instead of being cooled by the oil is on the contrary, heated by the oil.

Besides, the heating may lastly be harmful to the liquid itself. Consequently, a renewal is desirable from time to time and this is an unpleasant work which takes much time and cannot be easily carried out by the user himself. Another factor to be considered is that the minimum dimensions of the apparatus are also de-- According to the invention these drawbacks areobviated. For this purpose use is made of an X-ray tube in which the heat is not transferred to a cooler fastened to the anode and projecting from the tube but to the wall of the tube. This manner of heat transfer is described in U. S. Patent No. 2,228,384 dated January l4, 1941, and does not in itself constitute the invention.

The wall of the tubeis preferably provided with a metal part surrounding the anode and care is taken that'the anode has a good heatradiating surface and is fastened in such manner that no appreciable conduction of heat to other parts than the metal part of the wall can occur.

' According to the invention, a t ube of the said 7 type is connected to the metal wall of the housing, filled with an insulated liquid, in such heatconductive manner that the heat is transferred directly to the housing, that is to say without any appreciable conduction by liquid.

X-ray apparatus are already known in which the X-ray tube and the high-tension transformer are arranged in a common housing filled with oil and in which the heat. of the anode is carried ofi without the oil serving as conveying means, for example due to the cooler bein led through the wall of the housing. In this case the tube is wholly surrounded by oil and insulated by this liquid from the metal housing connected to earth. Since the anode is connected to the housingthe cathode has to be insulated for the full working voltage of the housing. This precaution also applies to the terminal of the'source of supply to which the cathode is connected and to the current-supply conductors. Because of this the advantage of a symmetrical arrangement has to be abandoned.

By conducting the heat according to the inventionv to the wall of the tube and grounding the latternot only electrically but also thermally a considerable saving in space and weight is obtained as compared with the known apparatus. In addition, in the device according to the invention it is only necessary to insulate for half of the tube voltage since the tube may be symmetrically arranged. relatively tothe grounded envelope.- 7

Also special apparatus are known in which an X-ray tube consisting for the greater part of metal forms one unit-with the transformer and in which only an insulating part which carries the cathode extends into the 011. These app ratus also could not be generally used since n practice apparatus are preferred which are symmetrically arranged and in which the tube may be readily replaced.

In particular if the tube and the shield do not constitute one separate part of the X-ray tube but the housing, in addition to the X-ray nents, as condensers, transformers, or valves it-is of importance that the tube can be easily "removed from the remainder of the In order to facilitate in this case the replace ment of the tube it may be fastened to the cover oi' the housing so that, together with this cover.

it can be removed from the housing after the mechanical connection between the cover and the housing, whichnatura-lly must be liquidtight, has been loosened.

In order to ensure proper conduction of heat from the tube wall to the housing the latter or the cover of the housing, may be providedw ith r s 15 to a plate I] which constitutes the cover oi a a saddle-shaped part which serves to support the tube, and one or more-metal clips provided which embrace the X-ray tube, clamping it against the saddle-shaped part. 'Ihese metal clips serve in this case also for the conduction or The heat-conductive contact from the wall of the X-ray tube to the wall of the housing, the

thermal short-circuit) is further promoted by surrounding the tube with an envelope con-- sisting or a suit substance .01 good heat-conductive material, for example lead. -The possible contact-surface or the tube wall with the tube and the metal-clips respectively is thus obtained. The soft material can'be easily forced against the parts with which it is in thus reducing interruptions in the contact surface to.

a minimum. a v

In the construction according to the invention the heat is carried-a'wa'yirom the wall of 'thetube directly to the housing. Thereis no perceptible diiterence in temperature between the tube wall and the housing and, since the whole outer surface oi the latter is available to transier theheat to the surroundings; itundergoesabut 1 slight heating.

Consequently, the insulating liquid serves exclusively as an insulator and does not act as means to'can-y oil the heat from the tube. It consequently remains oooland thus retains its good properties for a much longer time. In x-lay apparatus the conversion of electrical enersyintoheat is principally eiieotedby the x ray Thelossesintransrormersandothercom- Donents are but slight compared heat which is; developed inthe tube anddo not cause 8. 1 isa longitudinal sectbn' and I Fig. 2 is a cross-section oi a'a'X-ray apparatus comprising an x-ray tube. and a device 'ior' increasing the voltage. The x-rsy tube. together with the other components of the apparatus, is 75,

5 I. Glasspartsiandlotthewalloithetube aresealedtotheedgesoithemetalpameach ca yinganelectrodeoithetube.

- The cylinder-shaped, lead-covered metal part of the wall 01 the tube tits-into a depression 01 a metalbody l. Metalclipslandlembraoethe X-ray tube, clamping it against the saddle-' shaped part I so that 'a good heat conductive connection is obtained between the metal part oi the tubewall and the bodyl. The latterisiastened metal tank 22- and seals the latter hermetically. The tank 22 contains not only the x-ray tube but also two rectifying tubes 8 and I, two condensers ll and II and two heating-current transformers l2 and H. v

7 One electrode of the condenser II is connected 'tothe anode a of the x-ray tube andto'the cathode oi the rectifying tube I. trode is connected to-the cathode oi the tube 3 and to a current-simply conductor ll.

Oneelectrode of the condenser H isomnected to the anode of th'erectiiying tube l and to the cathode It or the x-ray tube. other electrode is connected totheanode oi'thego tube land to a current-supply conductor II.

The condensers and rectiners serve to increase the voltage applied so that the supp y voltage nced'be only P rt of the voltage of the-tube.

.The current transformer It has a primary 7 winding I which is energized from the exterior with a' low voltage, and two secondary windings II and II which are'insulated for high tension relatively to one another and to the Winding it. The incandescent cathode of the rectifying lotubelisenergizedbythewlndlngl'landthe incandescent cathode oi theimtifying tube I isenergized by thewindingll,

The current transformer. II has a primary winding I! which is energisedirom the exterior with a; low voltage, and a secondary 20 p which is insulated ior. high tension relatively" to thewinding |I.' incandesoentcathode otgenerated thereby,

6., but all the parts with which the insulatin liquid makes contact are but slightly heated. This is very advantageous for the preservation of the quality oi the liquid as an insulator and makes it possible for the apparatus to have smaller dimensions than it would be the case it theheat would have to be carried on through the liquid. It is true that a small loss of heat from the heating-current transformers and further components is absorbed by the liquid but it is too slight to cause a considerable increase of the temperature oi the liquid.

An apparatus such as described for a continuous power oi 100 watts may have a total length of 50 cm. (30 cm. without the projecting caps 23 and 24), a height of 25 cm. and a width of 12 cm.

Thelead layer 2 surrounding the metal part of the x-ray tube promotes a good heat-conduction between the tube and the body since the soft metal may be easily forced into the irregularities of the surfaces of themetal bodies.

It the side-walls oi the housing 22 or one at these walls are not of too thick metal they can slightly curve to the exterior in the case of expansion oi the liquid, resulting in a suflicient increaseof volume to permit the expansion of the liquid which is but slight due to the highly moderate heating.

What we claim is:

1'. In an X-ray apparatus, an X-ray tube comprising an evacuated envelope, a cathodeand an anode within said envelope, said envelope comprising a metal wall portion electrically insulated from and extending beyond the ends oi the anode and absorbing substantially all of the heat generated thereby, a metal container enclosing the x-ray tube, an insulating fluid in said container and metallic heat transmitting means directly conducting substantially all of the heat absorbed by said wall portion to said container. 7 a

2. In an x-ray apparatus, an x-ray tube comprising an evacuated envelope, a cathode and an anode within said envelope, said envelope comprising a metal wall portion electrically insulated irom and extending beyond the ends oi the anode and absorbing substantially all oi the heat generated thereby, a metal container enclosing the x-ray tube, an insulating fluid in said container, means securing said tube to a wall of said container, said means directly. conducting to said container substantially all of the heat wall and engaging the metal absorbed by said wall portion and comprising a metal member in thermal contact with the metal portion of the envelope and the wall of said container, said member having engaging surfaces conforming to'the suriaces of said metal portion of said envelope and to said container wall. 3. In an X-ray apparatus, an X-ray tube comprising an evacuated envelo a cathode and an anode within said envelope, said envelope comprising a metal wall portion electrically insulated from and extending beyond the ends oi. the anode and absorbing substantially all of the heat the X-ray tube, an insulating fluid in said container, means securing said tube toa wall of said container and directly conducting substantially all oi the heat absorbed by said. wall portion to said container, said means comprising a metal-saddle member secured to said container wall and to the metal portion of said envelope a metal container enclosing and a soft metal layer interposed between said saddle member and themetal portion of said envelope.

the X-ray tube,.an insulating fluid in said container, means securing said tube to a wall of said container and directly conducting substantially all or the heat absorbed by said wall portion to said container, said means comprising a metal saddle member secured to said container wall and tothe metal portion of said envelope and a layer oi lead metal interposed between said saddle member and the metal portion of said envelope.

5. In an X-ray apparatus, an X-ray tube comprising an evacuated envelope, a cathode and an anode within said envelope, said envelope comprising a metal wall portion electrically insulated' from and extending beyond the'ends of the anode and absorbing substantially all of the heat mit heat expansion of said fluid, said means com prising a concave deformable resilient wall portion of said container.

6. In an X-ray apparatus, an X-ray tube comprising an evacuated envelope, a cathode and an anode within said envelope, said envelope comprising a metal wall portion electrically insulated from and extending beyond the ends or the anode and absorbing substantially all of the heat generated thereby, a metal container enclosing the X-ray tube, an insulating fluid in said container, meanssecuring said tube to a wall of said container and directly conducting substantially all 0! the heat absorbed by said wall portion to said container, said means comprising a metal saddle member secured to said container velope and a metalclip member embracing the metal portion of said envelope and securing said tube to said saddle member.

'7. In an X-ray apparatus, an X-ray tube comprising an evacuated envelope, a cathode and an anode within said envelope. said envelope comprising a metal wall portion electrically insulated from and extending beyond the ends of the anode and absorbing substantially all of the 'heat generated thereby, a metal container enclosing the X-ray tube, an insulating fluid in said container, means securing said tube to a wall of said container and directly conducting substantially all of the heat absorbed by said wall portion to said container, said meanscomprising a metal saddle member secured to said container wall arid engaging the metal portion of said envelope and a metal clip member embracing the metal portlon of said envelope and securing said tube to said saddle member, and a layer of soft metal surrounding the metal portion of said envelope and in contact with said clip member and said saddle member.

BouwnRs.

portion 01 said'en-. 

